Prester John (also Presbyter John) was a legendary Christian ruler in India, combining the roles of patriarch and king. The legend of Prester John began in 12th century with two reports of visits of an archbishop of India to Constantinople and of a Patriarch of India to Rome at the time of Pope Calixtus II (1119-1124). These visits cannot be confirmed, evidence of both being second-hand reports.
Otto of Freisingen in his Chronicon of 1145 reports that in 1144, he had met, in the presence of Pope Eugene II in Viterbo, a certain Hugo, bishop of Gabala, who told him that Prester John was a Nestorian Christian, was descended from one of the Three Magi, and had defeated the Mohammedans in a great battle "not many years ago". After this battle, Prester John allegedly set out for Jerusalem to rescue the Holy Land, but the swollen waters of the Tigris compelled him to return to his own country. He was said to be enormously wealthy, his sceptre, for example, being of pure emeralds.
What is very definite is a letter, the Letter of Prester John, believed to be a forgery, which was supposedly written to the Byzantine Emperor Manuel I Comnenus (1143-1180) by Prester John, the King of India. The letter later came, copied, to the Holy Roman Emperor Frederick Barbarossa. This letter, appearing around 1165, which recounted many marvels of richness and magic, captured the imagination of Europeans and circulated in ever more embellished form for centuries and shortly after the invention of printing in printed form, being still current in the popular culture during the period of European exploration.
The letter included details (about St. Thomas, about peppers, and about elephants) which indicate that the writer (whoever he was) placed Prester John in India, possibly toward the eastern coast. Its details also bore close resemblances to fictional accounts of the life of Alexander the Great in India, mentioning things such as cannibals, rivers flowing from Paradise/Eden, pygmies and men without heads, which appear in both sources (see this article for further details).
The reports were so far believed that Pope Alexander III sent a letter to Prester John via his emissary Phillip, his physician, on September 27, 1177. More recent research has pointed to the recipient actually being a member of the contemporary Ethiopian royal house. Certainly, later, at the start of the 15th century, priests in Abyssinia were describing their country to Portuguese merchants as the Kingdom of Prester John. Whatever the truth, Phillip was never heard of again.
Several Asian tribes were identified with Prester John by travellers, but from the 14th century onward his empire was sometimes placed in Africa, and in the 15th and 16th centuries it became considered to be equivalent to the Christian kingdom of Ethiopia. Prester John was often identified as a descendant of the Magi, or a descendant of St. Thomas, who had supposedly founded an early (and therefore more pure) church in India.
When the Mongols invaded Palestine in the 13th century, the Christians inhabiting the remnants of the Crusader States also believed Genghis Khan was Prester John, coming to rescue them from the Muslims. In fact, in or about 1222 Genghis and his armies had met and fought the easter Asian Islamic forces to destruction. The Khan was averse to Mohammedanism and tolerant of Christians and this may have added to the comparison with the Prester. However others among the Mongols were less tolerant - the Prester John attribution finally settling on a Keriat tribe who had, indeed, become Nestorian Christians.
Another possible origin for Prester John is Toghrul Khan, a Nestorian Khan defeated by Gengis. The lingering belief in a Nestorian kingdom in the east accounts for several Christian embassies to the Mongols, in particular the one of William of Rubruck, who was sent to the Tartars by Louis IX in 1253.
Cartographers located the land of Prester John, variously, in Tibet (c.1507), in Africa (Carta Marina 1516) and then specifically in Abyssinia. Leutholf (1681) finally dismissed this as erroneous, but by then the legend had stimulated exploration and missionary activity throughout NE Africa, central Asia and China.
"Sir John Mandeville", writing c.1366, offers an extended and fanciful account of Prester John (although he never states he has visited the country in question). Thus he says that the rocks of the sea-bed drew iron to them, disabling any iron-nailed ship which approached. Prester John's land held 72 provinces, each ruled by a king. Seven kings served him directly at a time, on a rota basis, together with 72 dukes and 360 earls. His capital was at Susa; his throne there stood upon seven tiers, each of a precious stone: onyx, crystal, jasper green, amethyst, sardine (possibly sardonyx), carnelian and chrysolite. He also had a palace at Nysa. He had 3 archbishops and 20 bishops at his court every day, and his equivalent of the pope was the patriarch of St.Thomas. (Which would have been consonant with the legend that St.Thomas had journeyed to India and died there. Alfred the Great, in 833, sent 2 priests with gifts to St.Thomas' shrine.)
This article was initially extracted from Wikipedia.